Using an 18.1p illustrative margin for 365 days.
Battery-only storage
Can a home battery save money without solar panels?
Yes. A battery can buy electricity when it is cheap and supply the home when electricity is expensive.
The idea is sound. Whether the purchase is sound depends heavily on the installed price and the amount of energy the household can shift every day.
How it works
Charge cheaply overnight. Discharge during the expensive day.
A compatible time-of-use tariff offers one or more low-rate periods. The battery charges during those hours, then supplies household loads when the tariff rises.
This can suit listed buildings, conservation areas, shaded roofs and homes where panels are impractical. It can also provide backup power if the equipment includes a properly designed emergency-power function.
Backup is not automatic. Many ordinary battery installations shut down during a power cut unless dedicated backup equipment and circuits are installed.
The calculation
The tariff spread must survive battery losses.
Illustrative shifted-unit cost
If overnight electricity costs 8p/kWh and round-trip efficiency is 90%, delivering 1kWh later requires about 1.11kWh from the grid.
1.11 × 8p = about 8.9p delivered
If the avoided daytime unit costs 27p, the gross saving is about 18.1p per delivered kWh.
Actual efficiency varies with equipment, temperature, standby use and operating power. Supplier eligibility and rates must be checked before relying on any figure.
What that margin may produce
Daily use determines annual saving.
A fuller daily cycle, if the household actually needs the energy.
High use improves the opportunity but needs sufficient battery and discharge power.
Illustration only, before degradation, finance, maintenance or replacement. Tariffs can change.
The price problem
A £9,500 installation is difficult to recover through ordinary tariff shifting alone.
At £529 annual gross saving, simple payback on £9,500 is about 18 years. At £793 it is about 12 years. Those figures ignore battery degradation, possible repairs, tariff changes and the time value of money.
A lower installed cost, higher daily demand, wider tariff spread or valuable backup requirement can improve the case. A low-use household paying a premium battery-only price may never produce a convincing financial return.
This is why adding panels for a modest extra cost can transform the proposition: solar adds new energy rather than only moving purchased energy.
Before buying
Check the complete battery-only proposition.
✓ annual electricity consumption excluding standing charges;
✓ how many kWh are used outside the cheap window;
✓ usable—not nominal—battery capacity;
✓ continuous charge and discharge power;
✓ round-trip efficiency and standby consumption;
✓ tariff eligibility without an EV or solar array;
✓ warranty years, cycles and energy throughput;
✓ backup capability and essential-load limits;
✓ DNO notification or application requirements.
Tariffs
Do not buy hardware around one promotional rate.
Some tariffs require an EV, compatible charger, solar, a particular battery or supplier control. Others offer whole-home off-peak electricity without requiring the battery to be a specific brand.
Octopus Flux is designed around solar and batteries and includes a cheap early-morning charging period. EV tariffs such as Intelligent Octopus Go require an eligible vehicle under their terms. E.ON's Next Drive products likewise have eligibility and smart-meter conditions.
Use the tariff available to the actual household, including its peak rate, standing charge and export arrangement—not the cheapest number found in an advert.
Who may benefit?
Battery-only works best where demand is predictable and substantial.
Strong candidates include homes with high daytime and evening electricity use, electric heating, home businesses, resilience needs or roofs that cannot take solar. The battery must be used regularly enough to earn back its cost.
It is a weaker proposition for a low-use household, a property likely to move tariff frequently, or a system priced almost as highly as solar plus storage.
Current references
Check eligibility and live rates.
- Octopus Flux official tariff information
- Octopus smart-tariff terms
- E.ON Next Drive official tariff information
Guide checked 25 September 2026. Tariffs, eligibility and rates change. The 8p/27p calculation is an illustration, not a live tariff quotation.